Roderick macrae



(No Model.)

B. MACRAE. AUTOMATIC. SWITOH FOR ELECTRIC MOTORS. No. 453,287. Patented June 2,1891.

m5 NORRIS Finns cm, vuormuma, mar-uneven, u. c.

UNITED STATES PATENT OFFICE.

RODERICK MACRAE, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE DONALDSON-WIACRAE ELECTRIC COMPANY, OF SAME PLACE.

AUTOMATIC SWITCH FOR ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 453,287, dated June 2, 1891.

A Application filed August 27, 1890. Serial No. 368,213. (No model.)

To all whom it may concern.-

Be it known that I, RODERICK MAORAE, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Automatic Switches for Electric Motors, of which the following is a specification, reference being had therein to the accompanying drawlng.

This invention relates to certain :new and useful improvements in automatic switches for use upon electric motors; and it has for 1ts object, among others, to provide a simple and cheap automatic switch for use on small constant-current motors to prevent the armature from attaining too high a speed and injuring itself in case the belt breaks or the load is thrown off. The parts are so arranged that when a certain predetermined speed is attained the toggles close up and strike a lever which releases the switch which short-circuits the two poles of the motor.

Other objects and advantages of the invention will hereinafter appear, and the novel features thereof will be particularly pointed out in the appended claims.

' The invention is clearly illustrated in the accompanying drawing,which,withtheletters of reference marked thereon, forms a part of this specification, and in which I have shown in side elevation such parts as constitute or co-operate with my improvement.

Referring 110w to the details of the drawing by letter, A designates an armature of known construction {15, its shaft, supported in a suitable bearing C at the front, which bearing is carried by a fixed portion D or arm of the motor.

shaft between the two bearings a and serves to normally keep the said bearings separated at their maximum distance from each other, but which is compressed 'under abnormal condition.

Affixed to the part or arm D is an arm G,

the upper portion of which extends horizontally and its inner end is curved downwardly and outwardly, as shown. It is secured to the arm Din anysuitable manneras,f0rinstance, by a screw or bolt (1.

Depending from the arm G, near its outer end, is a block II, of insulating material, secured thereto in any suitable 1nanneras, for instance, by screw cand to said block are affixed the metallic contact-points I, which are connected by wiref with the poles or binding-posts g 7L of the motor,which are secured to a base-board J.

Pivoted to the outer end of the curved portion 6 of the arm G by suitable means, as the pivot i, is a lever K, the free end of which is connected with the outer end of the horizontal portion of the arm G by a spring L, connected with the two parts in any suitable manner. This lever K carries a contact-point j so arranged relatively to the contact-points I that when said leveris released and is pulled upward by the spring L the said contactpoint. will engage the points I and short-circuit the two poles of the motor.

M is a lever pivoted near its center, as at k, to the outer end of the horizontal portion of the arm G, with a vertical portion arranged to normally rest upon the upper face of the free end of the lever K and hold the same down against the power of the spring L. The upper portion of this lever M is inclined inward, as shown, and is designed to be actuated by the toggles as they are closed. I preferably provide at the outer portions of the toggles projections, as Z, to engage the said inclined arm when the speed exceeds a predetermined amount, although these projections may he sometimes omitted and the inclined portions of the lever M actuated by direct engagement of the toggle-levers.

The operation will be readily understood from the above description when taken in connection with the drawing, and a detailed description thereof is not deemed necessary.

What I claim as new is 1. The combination, with the armature, its

3. The combination, with the armature and its shaft and the toggle-levers thereon provided with project-ions Z, of the fixed contactpoints connected with the poles of the motor, thelever carrying the movable contact-points, and the pivoted lever arranged to engage said lever and to be actuated by the projections on the toggle-lever, as set forth.

l. The combination, with the armature, its shaft, the toggle-levers thereon, and the fixed arm G, curved at one end, of the lever K, pivoted to said curved end and carrying contactpoints, the spring L, connecting the free end of the lever K with the arm G, the fixed c011- tact-point carried by an insulated block on the arm G, and the lever M, pivoted to the arm G, with a vertical portion engaging the upper face of the free end of the lever K and its upper portion inclined to be engaged by the toggles under abnormal condition, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

RODERICK MAORAE.

\Vitnesses:

THos. KELL BRADFORD, H. K. BROWN. 

